This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Jason Mezey and Brooke LaFlamme are working on the structural equation modeling of pigmentation in drosophila. Pigmentation in drosophila is caused by melanin. Since melanin has a strong ESR signal, an estimate of total pigmentation for a single fly or average pigmentation for a sample of several flies from the same group can be directly done by recording the melanin signal. The method was expected to be more precise and less time-consuming than traditional visual estimate of the pigmentation extent under microscope.